Exemplary embodiments of the present invention relates to a semiconductor design technology, and more particularly, to a technology for terminating internal transmission lines of a semiconductor device.
As semiconductor devices are designed to operate at higher operating frequencies, it is important to ensure a sufficient data window size and timing margin when data is outputted at high speed.
FIG. 1 is a circuit diagram of a conventional semiconductor device.
Referring to FIG. 1, the conventional semiconductor device includes a pre-driving unit 11 and a main driving unit 12.
The pre-driving unit 11 generates a pull-up driving signal PU and a pull-down driving signal PD corresponding to an output data signal DATA_OUT, and transfers the generated pull-up and pull-down driving signals PU and PD to a first transmission line LINE1 and a second transmission line LINE2, respectively. Specifically, a first pre-driving unit PDRV1 generates the pull-up driving signal PU and transfers it to the first transmission line LINE1, and a second pre-driving unit PDRV2 generates the pull-down driving signal PD and transfers it to the second transmission line LINE2.
The main driving unit 12 drives a data input/output pad DQ in response to the pull-up driving signal PU and the pull-down driving signal PD transferred through the first transmission line LINE1 and the second transmission line LINE2. Specifically, a pull-up driving unit MDRV1 or a pull-down driving unit MDRV2 of the main driving unit 12 pulls up or pulls down the data input/output pad DQ to a power supply voltage VDDQ or a ground voltage VSSQ according to the control of the pull-up driving signal PU and the pull-down driving signal PD.
FIG. 2 is a waveform diagram of the pull-up driving signal and the pull-down driving signal in the conventional semiconductor device.
Specifically, FIG. 2 is a waveform diagram of the pull-up driving signal PU and the pull-down driving signal PD that are generated from the pre-driving unit 11 when the output data signal DATA_OUT is “0100101101,” and then transferred to the first transmission line LINE1 and the second transmission line LINE2.
Referring to FIG. 2, a first waveform 21 represents a case where data is outputted at low speed while the semiconductor device operates at a relatively low operating frequency of A Hz, and a second waveform 22 represents a case where data is outputted at high speed while the semiconductor device operates at a relatively high operating frequency of 2×A Hz. For reference, the second waveform 22 is a waveform of the pull-up driving signal PU and the pull-down driving signal PD when the operating frequency is two times higher than the first waveform 21.
If the operating frequency becomes high and data is outputted at high speed, 1 unit interval (UI) corresponding to the width of 1 data bit gradually becomes narrower. However, if the 1 UI becomes too narrow, the full swing of the signals cannot be achieved, as illustrated in the second waveform 22. If the full swing of the signals is not achieved during the 1 UI, pattern jitters may be generated. The pattern jitters operate as a factor to reduce an effective window size and timing margin.